Cost-efficient delivery of potable and/or industrially usable water is of growing importance. In many instances, potable water is shipped rather than treating non-potable water at the point of need due to treatment costs associated with the production of potable water. In turn, non-potable water at the point of need is often sent to disposal instead of being treated. For example, a substantial amount of water is generated and utilized in the production of crude oil and natural gas from subterranean formations. Such water (referred to in the industry as “produced water”) contains a wide variety of contaminants, including emulsified and dissolved hydrocarbons, inorganic and organic sediments, well management chemicals and numerous salts, such as salts of sodium, calcium, chloride, fluoride, barium, magnesium, nitrate, nitrite, bicarbonate sulfate, iron, and sulfite. Thus, produced water generally contains very high amounts of contaminants and is rarely treated to produce potable or industrially usable water. Rather, produced water is generally injected back into the earth via a disposal well, or is treated as minimally as possible to permit disposal.
When it is desirable to treat water, either to generate potable or industrially usable water and/or to decontaminate water for discharge into the environment, ion exchange systems are often used. Ion exchange systems have long been known for removing impurities from fluids. For example, ion exchange systems are used to purify a liquid product, to remove contaminants from an effluent, a waste stream, or the like, or to treat a liquid to render it useful for a particular purpose, such as desalination of sea water for purposes of providing water for human consumption. Generally, an ion exchange resin is used in the ion exchange system, typically in the form of small beads, to adsorb contaminants in the fluid. The resin eventually is saturated with contaminants and is characterized as “spent.” To minimize production costs, the resin is usually regenerated, generally by removing the resin from the system and treating it with one or more chemicals to remove the adsorbed material.
While effective, conventional ion exchange treatment systems have their downside. For example, regeneration of spent resin is typically carried out on a batch basis, during which fluid treatment and resin regeneration are carried out separately and in the same vessel. While batch procedures may be effective to remove the contaminants, batch processes suffer in that the flow of fluid to be treated must be stopped periodically in order to permit regeneration of the resin beads, effectively stopping fluid treatment. Furthermore, regeneration typically involves the consumption of large quantities of regenerants and, consequently, results in the discharge of large quantities of reject. Another drawback of conventional ion exchange systems is that pressurization may be required. Thus, there exists a need for improved ion-exchange systems, apparatus and methods.